Technological Field
The present disclosure relates to adjustment of a toner adhesion amount in an image forming apparatus.
Description of the Related Art
In an image forming apparatus adopting a roller charging system, a film on an outside of a photoreceptor is worn as the apparatus is used. This wear can be suppressed by transfer of a lubricant contained in toner to the photoreceptor. If an amount of the transfer of the lubricant to the photoreceptor is not constant in a main scanning direction, an inclination may occur in the wear of the film thickness of the photoreceptor in the main scanning direction.
An image forming apparatus uses one image density control (IDC) sensor for each color to be printed, for controlling a toner adhesion amount. The IDC sensor is realized by, for example, a reflective photosensor. More specifically, the image forming apparatus causes the IDC sensor to detect a toner adhesion amount adjustment pattern formed on an intermediate transfer belt, and adjusts an adhesion amount of each color toner with use of the detection result.
As described above, there may be a case where an inclination occurs in the wear of the film thickness in the main scanning direction. On the other hand, JP 2014-132318 A proposes a technique of appropriately correcting an adhesion amount by arranging a plurality of IDC sensors in a main scanning direction, reading a same toner adhesion amount adjustment pattern to calculate an average value of an inclination of each development characteristic, and adjusting image formation conditions such as development potential and charging bias on the basis of the calculation result.
Further, in a part that is not a detection target by the IDC sensor, a toner adhesion amount is not adjusted even if the photoreceptor is worn. This may cause an actual toner adhesion amount to fall below a target adhesion amount range. In such a case, a low toner density may be conspicuous in a formed image. On the other hand, for example, JP 2011-39105 A proposes a technique of arranging a plurality of IDC sensors in a main scanning direction. In this technique, deviations from respective target values are detected by reading a correction pattern with use of the plurality of IDC sensors, and a density is stabilized by using the IDC sensor with a larger deviation for density correction.
However, in the technique proposed in JP 2014-132318 A, increasing the number of the IDC sensors to be used for adjusting a toner adhesion amount and using toner adhesion amounts at many points require a long time for detection and analyzation of the result, creating a new problem of prolonging a time required for adjustment.
Further, in the technique proposed in JP 2011-39105 A, an IDC sensor having a larger deviation is used for density correction. Therefore, when an inclination of wear is large in the main scanning direction of the photoreceptor, the toner adhesion amount may not always be appropriately corrected.